The buff doesn't care about weapon categories as far as I can tell - two handed weapon models can go over 1h weapons and vice versa. Polearms can become swords or maces or fist weapons. (In fact, it can even put the wrong fist weapon model on a hand, so that it's clearly backwards.) If you switch the weapons out, the effect fades but the buff remains and it can bug out so that you have to clear the buff in order to use the effect again. But it does allow you to basically switch between a variety of weapons in your main bag if you like variety, or it allows you to effectively use legendary weapons in your current transmog look, if you're a warrior.

As an example, here's Bo-Ris with Thunderfury, Blessed Blade of the Windseeker over it. It seems that Unique restrictions still apply, as even when I only had Thunderfury in my bag, I could only get one weapon to take on its appearance.

The glyph is specific in its phrasing for a reason - if the weapon is anywhere other than your original backpack, it will not work. At present, the only restriction seems to be that you have to be able to equip the weapon. For example, the PvP weapons from the original ladder system do in fact work with the glyph.

This isn't a glyph that has any sort of effect on PvE or PvP balance, it provides no character power at all, and its not even really original to warriors, being an upgraded version of the Glyph of Felguard, and I don't care. It's awesome. Whether you like variety (I often go remog just my weapons, so now I'll just carry the weapons I like the most), want to use a weapon with a restriction like the PvP weapons or legendaries, or just want something fun and new other classes don't have I highly recommend this glyph for all warriors.

I'm going to finally get to raid with my Thunderfury, guys. I'm so stoked I cannot even tell you.